How to use your mobile phone to measure the air quality in your surroundings

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Breathe clean air It's something we take for granted until someone from outside tells us, "Wow, this place is really polluted." If you live in a big city, you'll be familiar with that feeling of stuffiness and pollution, especially on dry days or during periods of heavy traffic, when air quality plummets and our health suffers without us even noticing.

The good news is that today we carry it in our pockets A tool that allows us to know, almost instantly, the quality of the air we breathe: the mobile phone. Thanks to official measurement networks, research projects using smartphone cameras, and a host of other initiatives, we can now see the effects of air quality. free appsIt is possible to check from the comfort of your sofa at home - or by taking a walk - whether it is advisable to open the window, go for a run or better to wait for the atmosphere to improve.

From "dumb" devices to the smartphone that does (almost) everything

When Apple introduced the first iPhone in 2007 It sent a very clear message: the era of devices that only served one purpose was over. Since then, the mobile phone has become a digital Swiss Army knife with which we read, play games, watch series, listen to music, work, and, of course, consult detailed environmental and weather data.

We owe that versatility to the applications. which we download from the official iOS and Android stores. Many of them connect directly to the same meteorological services and monitoring networks used by public administrations, television stations, and official agencies to produce their daily weather and pollution reports.

However, it is important to be aware of one significant limitation.Mobile phones do not come equipped with specific air quality sensors like those found at official monitoring stations. They cannot "smell" ozone or "see" fine particulate matter on their own, at least not directly and with regulated guarantees.

What they do – and very well – is exploit their connectivity Mobile and Wi-Fi are used to consult real-time servers where data from networks of stations, satellites, and air quality models are stored. The mobile phone thus becomes the window that shows us whether we are experiencing a day with clean air or a pollution episode that should be taken seriously. To optimize this connection and reduce data loss, it is advisable to pay attention to the mobile and Wi-Fi connectivity available.

What is a particle meter and how is air quality monitored?

In Spain, the installation and management of air quality monitors This responsibility falls to the autonomous communities and many municipalities. Within Spain alone, hundreds of monitoring stations are already operating—more than 600 according to the latest figures—under specific regulations that define what constitutes healthy air and when pollution alerts should be activated.

These stations do not just "smell" the environmentThese systems combine gas analyzers, particle collectors, meteorological sensors, and mathematical models. They take into account factors such as industrial activity, traffic, data from low-cost sensors, information from satellites (e.g., Copernicus), the local climate, topography, and pollutant dissipation patterns.

Among the most closely monitored pollutants are several old acquaintances.: nitrogen oxides (NOx), mainly linked to high-temperature combustion in road traffic; tropospheric ozone (O3), which is formed when NOx and volatile organic compounds (VOCs) react; sulfur dioxide (SO2), associated with the burning of sulfur-containing fuels and certain industries; and the well-known particulate matter (PM10 and PM2.5), which is very fine and capable of reaching deep into the respiratory system.

A key part of this surveillance is the network of distributed stations across the territory. For example, in the Basque Country Autonomous Community there is an air quality monitoring network with 55 stations equipped with analyzers for SO2, NO, NO2, tropospheric ozone, CO, benzene and particulate matter (PM10 and PM2.5), as well as meteorological sensors that help to interpret how pollutants disperse or accumulate.

In addition to the fixed stations, there are also mobile units Vans, trailers, and other equipment designed to carry out measurement campaigns at specific locations. An example of this can be found in Irun, where a mobile unit belonging to the Basque Government's Control Network has been installed to collect data prior to the creation of a low-emission zone in the city.

Practical example: mobile stations and low emission zones

In the case of Irun, the City Council is promoting A low-emission zone to reduce traffic-related pollution. To design it effectively, they first need to know in detail what the air quality is like at different points and times of the year, and that's where the mobile monitoring unit comes in.

This mobile station measures continuously The data is then sent to the Basque Government's Air Quality Control Service. At the end of each campaign, a report is prepared and sent to the City Council, outlining trends, predominant pollutants, and any isolated incidents that may require additional measures.

The plan includes two measurement campaigns The studies were conducted at two different locations, with each study lasting approximately two months, aiming to cover seasons with varying weather conditions. This yields comparable data series for winter, spring, and other seasons, allowing researchers to observe how pollutant behavior changes.

In one of the locations, on the corner of Paseo Colón and Avenida GipuzkoaThe objective is to measure parameters closely linked to traffic (e.g., NO2 and particles from vehicles) during periods such as November-January and March-May, when atmospheric conditions are very different.

The second location, yet to be defined, is envisioned as a more open environment.away from heavy traffic and serving as a "background". There, the focus is on measurements not associated with traffic, that is, on seeing what levels of pollution exist at baseline due to more diffuse or distant causes, such as the transport of masses of polluted air or Saharan dust.

This mixed network model (fixed and mobile stations) It's not just useful for planning low-emission zones; it also makes it easier for citizens to access up-to-date data. It's precisely these networks, along with other systems, that power many of the apps we use on our phones to find out if the air is "good enough to go for a run" or rather "to stay home."

How all that information reaches the mobile phone: sensors, time series and platforms

Air quality data doesn't just stay locked away in a drawerThe monitoring networks continuously send their measurements to management platforms that allow the generation of time series and graphs of all measured parameters. It is possible to choose very short intervals, as short as five minutes, or long periods of months or years.

Thanks to these series it is possible to follow individual evolution of each component (for example, PM2.5 or ozone) and see how they change with the time of day, the day of the week, or the seasons. Peaks during rush hour, summer episodes with lots of sun and little wind, or incursions of desert dust are all clearly visible at a glance.

When several curves are represented on the same graph For example, correlations and patterns can be detected quite clearly between particulate matter and nitrogen dioxide, along with wind speed. This is where you can see how a gust of wind clears the air or how a temperature inversion spikes surface levels.

Some home air quality monitors, such as certain air-Q modelsThey integrate several sensors and allow precisely that: generating long time series, visualizing trends and detecting small changes in the indoor environment, something very useful for sensitive people or for those who want to control the air in their home or office.

Much of this data eventually becomes available on open platforms, transparency portals, or international meteorological services. These are the databases that many air quality and weather apps we install on our phones consult, combining official information, satellites, models, and, in some cases, collaborative networks of low-cost sensors.

Cutting-edge research: using your mobile phone camera as a scientific tool

Beyond displaying data on screen, the mobile phone can also help to measure directly certain pollutants thanks to their smartphone cameraA good example is the research of the AQUIMA group (Chemical Analysis of the Environment) of the University of Extremadura, coordinated by the professor of Analytical Chemistry Eduardo Pinilla Gil.

His work focuses on the detection of PM10 particles (those with diameters of 10 microns or less) and tropospheric ozone in the air using low-cost methods supported by mobile phones. This line of research forms part of the doctoral theses of scientists Selena Carretero-Peña and María Cerrato-Álvarez.

The proposed technique seeks to support official monitoring This is done through digital analysis of images of daily samples captured with a smartphone camera. The idea is that the expert will have, almost instantly, an estimate of the concentration of particles or ozone in a specific area, which is then confirmed with more detailed laboratory analysis.

The procedure is ingenious but simple in conceptThe particles or ozone are collected on filters or pads (for example, fiberglass), placed inside a box designed to maintain reproducible lighting conditions, and a photograph is taken with a mobile phone. From there, the color space of the image is digitally analyzed and correlated with the concentration of the pollutant.

In the case of tropospheric ozone, the key lies in the degradation of a colorThe researchers impregnate a passive substrate with indigotrisulfonate, a blue reagent that fades when it reacts with ozone. The more ozone the filter absorbs, the more the blue color degrades; by measuring this loss of intensity with a smartphone camera, the concentration of ozone in the air can be estimated.

For PM10 particulate matter, the challenge is greaterThis is because the composition of the particles is very diverse: they include heavy metals, volatile organic compounds, and materials of natural or anthropogenic origin. This makes the color changes more complex to interpret, but promising results have been obtained through image analysis and appropriate calibrations.

These studies have been published in scientific journals such as Sensors, where the estimation of PM10 levels from the digital analysis of filter images captured with a smartphone is detailed, and in Microchemical Journal, where the measurement of tropospheric ozone by image analysis of pads with indigotrisulfonate is described.

A major advantage of these techniques is their low cost and speedThis is because they allow working with samples taken in urban and rural locations integrated into networks such as the Extremadura Network for the Protection and Research of Air Quality (REPICA). AQUIMA has been providing scientific and technical support to this network for years through an agreement between the University of Extremadura and the Regional Government of Extremadura.

Thanks to this collaboration, local sources have been identified. of particulate emissions, but also of remote sources such as dust from the Sahara. Monitoring over a year, combining passive sampling and digital image analysis with smartphones, has shown that the method is a useful tool to support traditional air quality analyses.

Apps to check air quality from your mobile phone

While the investigation progresses, here's what we already have on hand These are very powerful applications that connect to official networks and other systems to show us air quality indices, forecasts and real-time alerts from our mobile phones.

One of the most comprehensive options is The Weather Channel's official appAvailable for iOS and Android, and backed by a prestigious international weather portal, this app not only offers weather forecasts for virtually any location on the planet, but also provides highly detailed information on extreme weather events.

Within the application we find rainfall data It includes forecasts, hourly temperature updates, warnings for heavy rain, snow, or extreme heat, as well as a hurricane warning center. It even incorporates local information related to the Covid-19 pandemic and a curious section called "Seasonal Center."

That “Seasonal Center” graphically summarizes the type of day We'll find out: whether we'll need umbrellas, whether it will feel cold or sticky, whether there will be a lot of mosquitoes, and what UV index level to expect. It's a pretty user-friendly way of translating technical data into something anyone can understand.

Regarding air quality, The Weather Channel dedicates a specific section to it. with seven-day forecasts and indicators that warn of the presence of pollen or mold in the air. They call this section "Respiratory Comfort Today," a kind of thermometer of how comfortable our lungs will be throughout the day.

The app also allows you to go into detail about the main pollution zone. and provides a general summary using a percentage and color indicators: green for good situations, yellow for regular conditions and red for more dangerous scenarios, all based on pollutants such as NOx, O3, VOC, SO2, PM10 and PM2.5.

The Weather Channel offers a freemium modelThe annual subscription costs around €32,99, with monthly plans starting at €0,99. For those who want up-to-date data, no ads, and a full suite of weather and air quality features, it could be a worthwhile investment.

If you prefer something simpler and focused only on pollutionBoth Android and iOS offer a multitude of apps dedicated exclusively to displaying air quality indices. Among the highest-rated are BreezoMeter, AirVisual, and Plume Labs, all with a clear focus on respiratory health and quick consultation.

AirVisual: an example of a free and very complete app

AirVisual, available on both iOS and AndroidIt has carved out a significant niche, even receiving awards on Google Play as one of the best apps in its category. Its objective is very straightforward: to tell you, at a glance, whether the air around you is clean or particularly polluted.

To achieve this, AirVisual combines data from thousands of sensors Environmental quality data deployed by cities and countries with public access, as well as historical data, forecasting models, and other official sources. It covers more than 10.000 cities in over 100 countries, with a truly extensive database.

With the app you can track in real time of PM2.5, PM10, ozone, nitrogen dioxide, sulfur dioxide, and carbon monoxide concentrations. All of this is accompanied by a unified air quality index that indicates whether the situation is good, moderate, or unhealthy for different population groups.

One of its strengths is its attention to vulnerable groups.such as people with asthma or other respiratory illnesses. The app offers specific information and tailored recommendations: when it's best to avoid strenuous outdoor activity, when it's advisable to close windows or use air filters, etc.

If you're curious, it also allows you to "travel" around the map and see what the pollution levels are like in other cities around the world in real time. It's a very visual way to become aware of the extent to which some areas have chronic problems while others have very clean air.

In addition to the pollution section, AirVisual includes basic weather data such as temperature, humidity, current conditions (sun, clouds, rain) and forecast. This way you can combine the decision of whether to take an umbrella with whether it's a good day to go for a run or better to opt for the gym.

The app is free and, according to its creators, has no intrusive advertising.It includes an informative section that explains in plain language what PM2.5 or other pollutants are, how they affect health, and what measures we can take on a daily basis to reduce our exposure.

Another interesting detail is its integration with wearables.AirVisual offers compatibility with Apple Watch, allowing you to check air quality directly from your wrist. A quick glance at your watch before leaving home is all it takes to decide whether you need a mask or if the air quality is good.

Data, health, and everyday decisions: why watching the air matters

All this infrastructure of measurement networks, scientific projects and mobile apps It has a very clear objective: to enable us to make better everyday decisions based on real data about the air we breathe. This isn't just about technological curiosity, but about public health.

Pollutants such as PM2.5, NO2 or ozone are not visible to the naked eyeHowever, they are linked to respiratory and cardiovascular problems, as well as an increase in hospital admissions during periods of high pollution. Knowing when levels spike allows the most vulnerable people (children, the elderly, and those with pre-existing conditions) to better protect themselves.

At the same time, aggregated data serves the administrations to design mobility policies, low-emission zones, protocols for pollution episodes, and long-term plans to reduce emission sources. Mobile technology helps translate this background work into useful information for the average citizen.

Today we can combine them all in one phone Time series graphs from monitors, official alerts from surveillance networks, quick estimates made with smartphone cameras in research projects, and apps like The Weather Channel or AirVisual that package all that complexity into simple interfaces.

Without the user needing to be an expert in atmospheric chemistryThe mobile phone tells you if the air is "green" or "red" today, what pollutants are present, how the situation may evolve in the coming days, and what specific measures you can take to minimize the impact on your health and that of your family.

In a context where air pollution remains one of the major environmental challenges In our cities, harnessing the potential of smartphones to understand and monitor air quality in our environment has become almost as basic as checking the rain forecast before going out without an umbrella.